Heterogenous catalysts have a variety of known applications, in diverse fields including commodity chemicals and fine chemicals. It has long been recognized, however, that the catalytic activity and/or selectivity of heterogeneous catalysts can vary substantially due to many factors. Factors known to have a potential effect on catalytic activity and/or selectivity are described, for example, by Wijngaarden et al., “Industrial Catalysis—Optimizing Catalysts and Processes”, Wiley-VCH, Germany (1998).
Combinatorial (i.e., high-throughput) approaches for evaluation of catalysts and/or process conditions are also known in the art. See, for example, U.S. Pat. No. 5,985,356 to Schultz et al., U.S. Pat. No. 6,004,617 to Schultz et al, U.S. Pat. No. 6,030,917 to Weinberg et al., U.S. Pat. No. 5,959,297 to Weinberg et al., U.S. Pat. No. 6,149,882 to Guan et al., U.S. Pat. No. 6,087,181 to Cong, U.S. Pat. No. 6,063,633 to Willson, U.S. Pat. No. 6,175,409 to Nielsen et al., and PCT patent applications WO 00/09255, WO 00/17413, WO 00/51720, WO 00/14529, each of which U.S. patents and each of which PCT patent applications, together with its corresponding U.S. application(s), is hereby incorporated by reference in its entirety for all purposes. Considered individually and cumulatively, these references teach the synthesis and screening of arrays of diverse materials, and generally, of spatially-determinative arrays of diverse materials. Typical approaches involve primary synthesis and screening (high-throughput “discovery” screening) followed by secondary synthesis and screening (more moderate-throughput “optimization” screening), and optionally, followed by tertiary synthesis and screening (e.g., typically traditional “bench scale” screening). These references also describe screening strategies in which compositionally-varying arrays are prepared (e.g., as part of a primary or secondary screen) first with broadly-varied gradients. Subsequently, “focused” libraries comprising more narrowly-varied gradients are prepared and screened (e.g., at the same level of screen) based on the results of the first screen. Such libraries or arrays of diverse materials such as catalysts can comprise binary, ternary and higher order compositional variations. See, for example, WO 00/17413 (as well as its corresponding U.S. application, Ser. No. 09/156,827 filed Sep. 18, 1998 by Giaquinta et al.) and WO 00/51720, (as well as its corresponding U.S. application, Ser. No. 09/518,794 filed Mar. 3, 2000 by Bergh et al.), each of which U.S. and PCT applications are hereby incorporated by reference in its entirety for all purposes. High-throughput process optimization, including process optimization in parallel flow reactors has also been described. See, for example, WO 00/51720, (as well as its corresponding U.S. application, Ser. No. 09/518,794 filed Mar. 3, 2000 by Bergh et al.), and additionally, U.S. patent applications Ser. No. 60/185,566 filed Mar. 7, 2000 by Bergh et al., Ser. No. 60/229,984 filed Sep. 2, 2000 by Bergh et al., Ser. No. 09/801,390 filed Mar. 7, 2001 by Bergh et al., and Ser. No. 09/801,389 filed Mar. 7, 2001 by Bergh et al., each of which U.S. and PCT applications are hereby incorporated by reference in its entirety for all purposes.
The efficiency of a catalyst discovery program is, in general, limited by rate-limiting steps of the overall process work flow. Additionally, high throughput approaches still require substantial efforts to explore vast compositional space. As such, current approaches, while offering substantial advances over previous traditional, lower-throughput approaches, can still be improved with respect to overall efficiency. Hence, there is a need in the art for improved overall research work flows for developing and evaluating heterogeneous catalysts for a particular reaction of interest. In particular, a need exists for more efficient, meaningful approaches for identifying new heterogeneous catalysts.
More specifically, a need exists for improved preparation protocols for heterogeneous catalysts. Although substantial advances have been made with respect to parallel synthesis of catalyst candidate materials, and with respect to reaction-based screening of such catalyst candidates, relatively fewer advances have focused on pretreatment of heterogeneous catalysts—after synthesis of the catalysis material or precursor thereof and before screening thereof. Typical post-synthesis catalyst treatment can include chemical treatment (e.g., precursor decomposition, oxidation, reduction, activation), physical treatment (e.g., calcining, washing), and/or mechanical treatment (e.g., grinding, pressing, crushing, sieving, and/or shaping).
Mechanical pretreatment approaches have been effected to date for combinatorial catalysis research using conventional approaches. For example, Senkan et al. reported the preparation of a combinatorial array of shaped catalysts (pellets) using conventional, serial die-pressing. See S. Senkan et al., “High-Throughput Testing of Heterogeneous Catalyst Libraries Using Array Microreactors and Mass Spectrometry”, Angew. Chem. Intl. Ed., Vol. 38, No. 18, pp. 2794-2799 (1998). Grinding approaches for catalyst preparation are also known in the art, including both serial and parallel grinding protocols. (See, for example, Obenauf et al., Catalog of SPEX CertiPrep, Inc. (Metuchen, N.J.) pp. 28-39, 90-91, 104-105 and 114-119 (1999)). Schuth et al. disclose a loading device for synthesis of an array of catalysts, where the loading device is adapted for parallel transfer of the synthesized catalysts to a parallel flow reactor through a communition device. (See EP 19809477 A1). However, such conventional pretreatment protocols, such as the conventional serial pressing approaches, are not efficient enough for preparing arrays comprising larger numbers of catalysts. Moreover, conventional grinding or communiting approaches, although parallelized, suffer from other deficiencies. Such grinding approaches, as exemplified for example by the aforementioned communition protocols of Schuth et al., result in a to-be-tested catalyst candidate that includes a broad, uncontrolled distribution of catalyst particle sizes, including catalyst particle fines. Variations in the particle size distribution of candidate catalysts—as compared between reaction vessels (or channels) of a parallel reactor—can affect catalyst performance and, additionally or alternatively, can affect the flow-characteristics when screening the catalysts in a parallel flow reactor, such that in either case, direct comparison of catalysts between reaction vessels or channels is compromised. As such, there remains a need in the art to overcome such deficiencies.